Compared to the rest of the San Diego market, the National City submarket has lower rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 5 listings have come on the market, which means office spaces most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 220% of the listings in the National City are subleases, so you might be able to sign a shorter term by taking over a previous lease. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
Even though the median size is 3,010 sqft, there are still 0 spaces below 2,000 sqft. Most properties in this area are close to 2 stories. Most buildings in this area were built in 1974 and are Class B.